From the past, balloon catheters have been used with percutaneous transluminal coronary angioplasty (PTCA). A balloon catheter is equipped with a shaft through which a guide wire is inserted, and a balloon attached to the front end section of the shaft, and by supplying fluid into the balloon, the balloon is expanded at the stenosis portion of the blood vessel, and the stenosis portion is pushed open.
For the stenosis portion of the blood vessel that is pushed open by the balloon, with plain old balloon angioplasty (POBA), by pushing against the blood vessel wall a balloon for which the internal pressure of the balloon has been raised, the blood vessel wall is plastically deformed, and blood vessel expansion is realized.
However, with plain old balloon angioplasty, the problem of the blood vessel constricting again after treatment may occur. One reason for this is possibly due to the fact that the blood vessel wall is merely temporarily crushed by the pushing pressure of the balloon, and after the restriction by the balloon is released, it gradually recovers its original shape. As other reasons for restenosis, we can additionally list intimal thickening, negative remodeling or the like.
Also, when performing expansion of a stenosis portion using a balloon, similarly, blood vessel wall injury due to applying pressure is also a problem. Specifically, the stenosis portion is not necessarily flexible, and is typically harder than the other parts of the blood vessel, so sufficient pressurization of the balloon to push open the stenosis portion is required. However, when the pressure of the balloon is made high, there is the risk of injury occurring into the deep layer of the blood vessel, which is undesirable, and there was the risk of the blood vessel becoming stenosis again during treatment of the injury.
As one means of addressing these problems, for example in Japanese Published Patent No. JP-B-2535250 (Patent Document 1), a balloon catheter is proposed by which it is possible to realize deformability during expansion, and shape maintainability after expansion by adjusting the temperature of the blood vessel wall. Specifically, by heating the fluid inside the balloon and pushing the blood vessel wall open while warming it, it is possible to increase the flexibility of the blood vessel wall during expansion of the stenosis portion, so injury to the blood vessel due to expansion is prevented and restenosis is also avoided.
However, with the balloon catheter noted in Patent Document 1, a laser light absorbing heating tube heated by laser light is a braided structure made of stainless steel or the like, so it is easy for the flexibility to be insufficient, and it was difficult to ensure sufficient deformation following capability in relation to the blood vessel shape. In fact, fluid is made to be supplied inside the balloon through tiny gaps of the laser light absorbing heating tube with a braided structure, so it was necessary to spend a long time for balloon expansion deformation, and there was the problem that the surgery time became long, and this placed a big burden on the surgeon and the patient.
In addition, the front end fitting which adheres the front end section of the laser light absorbing heating tube is made of metal, and the front end fitting has a structure by which it is exposed to the outside (blood vessel interior), and the balloon and a third tube are also adhered to the front end fitting. Because of that, there is the risk that the front end fitting heated by laser light will contact the blood vessel wall and injure the blood vessel wall, and also the risk that the front end fitting will heat the balloon and third tube more than is necessary, bringing the risk of a decrease in durability or an injury.
Also, with Japanese Published Patent No. JP-B-2864094 (Patent Document 2), proposed is a constitution by which the balloon expansion speed is quickened by supplying fluid into the balloon through a through hole provided on the laser light absorbing heating tube. However, with the constitution noted in Patent Document 2 as well, the laser light absorbing heating tube has a metal braided structure, and in addition, a double structure part is provided on the laser light absorbing heating tube, so an increase in flexibility of the laser light absorbing heating tube was not yet realized.
Providing a gap in the braided structure of the laser light absorbing heating tube and increasing the flexibility of the laser light absorbing heating tube is also possible, but by doing that, when fluid is heated using laser light, there is the possibility of laser light leaking to outside the heating member. As a result, the heating efficiency by the laser light decreases, and there was the risk of a decrease in durability due to irradiation of laser light on the shaft or balloon.